2026 Interview Preparations

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Java 8 vs Java 11 vs Java 21

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Java 8 : Lamda expressions, Functional Interfaces, Default and Static interfaces, Streams, Completable features and New Date and time functions are introduced

Java 11 :  Local Variable syntax changes in Lamda,  Enhanced Streams and Collections concepts and HttpClient is introducted 

Java 21 : Virtual Threads, Pattern Matching in swith, Record Patterns and Sequence Collections are introduced 

Java 25 : Collection Performance, Stream preformance, Concurrent & Runtime Performance and I/O Security Enhancements. 

Immutable Class : A class which is not having setters and who's instance cannot be change after they are created.

• Declaring a final class 
• Make all fields are private 
• Make all fields are final.
• Donot provide the setters. 

Advantages of Immutable class : 

• Thread safety
• Security & Consistency 
• Reliable Hash keys

Microservices Design Patterns : 

Circuit Breaker DP : 

Retry Design Pattern : 

Rate Limtter Design Pattern : 

Saga Design Pattern : 

Event Driven Approach Design Pattern : 

Domain Driven Pattern : 

Database Design Pattern : 

Indentity Design Pattern : 

Security : 

Feign Client vs Rest Client : 

The primary difference is that Feign Client is declarative (you write an interface and let the framework generate the HTTP code), while a Rest Client is programmatic/fluent (you manually write the steps to build and execute the request).